This invention claims priority based on the following provisional applications whose teachings are incorporated herein by reference: (a) provisional application Ser. No. 61/516,004 filed Mar. 28, 2011 and titled PITCH DRIVEN WAVE ENERGY CONVERTER (PDWEC); (b) provisional application Ser. No. 61/516,003 filed Mar. 28, 2011 and titled MULTI-MODE WAVE ENERGY CONVERTER SYSTEM; and (c) provisional application Ser. No. 61/516,025 filed Mar. 28, 2011 and titled HYDRAULIC SPRING.
This invention relates to the connection of a (marine) cable carrying electric power and signals to a marine vessel, where the cable carries power and signals between the marine vessel and points external to the marine vessel.
The invention may be illustrated with reference to a wave energy converter (WEC) buoy, but it should be understood that it is applicable to any marine vessel. For example, wave energy conversion (WEC) systems or WEC buoys used to produce electric power need to connect to an underwater electrical power cable in order to export the power they produce to a power grid or other type of power distribution facility. Likewise, many types of marine applications require an electrical cable connection to a marine vessel. For example, boats or ships often need to connect to an electric power cable to receive electrical power for the powering of on-board equipment. Also, for example, many buoys (meteorological, oceanographic, etc.) have underwater sensors or equipment that need power transmitted to them and electrical signals received from them.
The point of connection of the underwater electrical cable to the marine vessel is often a point of stress to the underwater cable. In cases where the motion of the marine vessel is extreme (i.e. it heaves, pitches, rolls and/or yaws violently), the cable connection is a common point of failure. Numerous inventions and techniques exist to minimize the bending of cables at the point where the cable connects to the vessel (see U.S. Pat. Nos. 6,039,081, 7,695,197). Most of these concepts involve tapered sheaths around the cable and/or complex, articulated, interconnected bend limiting devices at the point of connection. These concepts still involve some flexing of the marine (or underwater) cable.
Known prior art bend restrictor devices and techniques, while effective at reducing the level of stress on cables, do not eliminate the cable flexures sufficiently and therefore do not eliminate the need for frequent servicing or replacement of the underwater cables, often at great expense.